In (Chicken) Scheme

This is the implementation I actually use every day: it proved to be the
fastest in terms of startup and displaying results. This why, when I added a
bit of functionality to the tool, I did it only in this implementation.

There are also half-working implementations in Dylan and Nimrod, which
probably could outperform Chicken Scheme, by the way. There was a bug in Dylan
HTTP client library (fixed now) which caused me to stop working on this
implementation and I never get back to it. It's different for Nimrod: I
started writing another implementation of this tool, but then I realized I'd
like to have a currency converter instead and went with it...